The present invention relates to a battery voltage alarm apparatus for use in a paging receiver and the like.
In a conventional radio paging system, subscribers are sorted into a plurality of groups, a plurality of receiving units are assigned with individual identification numbers and paged by using the identification numbers, and each signal unit drives, upon receipt of a paging signal, an announcing circuit to cause it to raise a ringing or other announcing means which informs the user of the occurrence of paging. In this system, it is preferable that paging be confirmed without fail even when the user is staying at any place and in the paging receiver, detection of a decrease in voltage of a power supply battery and consequent exchange of the battery at good timing are of a very important procedure for the sake of maintaining receiving sensitivity. Accordingly, the battery voltage detecting function is so designed as to raise a battery low voltage alarm (hereinafter simply referred to as LVA) of continuous ringing or other announcing means so that the user may be urged to exchange the battery. The LVA is one of various kinds of alarms, including reception announcing means.
However, the conventional LVA faces the following problems.
(1) When power supply voltage is decreased so as to raise an alarm during a user's sleep at night or during a long absence of the user, the alarm is noticed by the user and yet the LVA is continued until eventual complete exhaustion of the battery and consequent interruption of the alarm, with the result that the user cannot be informed of the timing for battery exchange. Taking the occurrence of a decreased voltage occurring during a user's sleep at night, for instance, the alarm must be raised continuously for about 7 to 10 hours before the user wakes, but it is almost impossible to continue the alarm for such a long time with a battery having a low or decreased voltage.
(2) If the LVA is mistaken for a paging alarm and resetting is effected, then the LVA will never be raised again and the timing for battery change will be missed.
The present invention intends to solve these problems.